924 Elementary Problems and Answers in Solar System Astronomy

Chapter 5. Other Planets, Their Satellites, and Rings

* * * CHAPTER 5 Other Planets, Their Satellites, and Rings 623. Which one of the nine major planets is missing from the following list: Mercury, Uranus, Pluto, Earth, Saturn, Mars, Jupiter, Venus? 624. The brightness of a planet of a given size and albedo as seen from the Sun varies (a) directly as the square; (b) inversely as the square; (c) directly as the three-halves power; (d) inversely as the fourth power of its distance. 625. The radiative equilibrium temperature of an inert object in space is directly proportional to the fourth root of the intensity of light that illuminates it. Starlight is less intense than sunlight at 1 AU by a factor of 1 X 108 • Calculate the temperature of an object in interstellar space, remote from any star, by comparison with the temperature of the Earth. 626. The nine major planets of the solar system are often classified into two types: terrestrial and Jovian. What is the basis for this classification and which planets are which? Into which classification would the minor planets fall? 81 82 / Other Planets, Their Satellites, and Rings 627. Which one of the following is a "terrestrial" planet? (a) Jupiter; (b) Uranus; (c) Neptune; (d) Mars. 628. Name the five planets (other than the Earth) that can be seen by the unaided eye at some time during a year. 629. Of what planet or planets are all of the following statements true? (1) It moves along its orbit in a counterclockwise sense as viewed from the northern celestial pole. (2) Its rotational period is less than thirty hours. (3) Its mass is greater than that of the Earth. (4) It has more than one natural satellite. 630. All of the following four statements are true for only one of the nine major planets. (a) Its axis of rotation is inclined at less than 30 degrees to the normal to its orbital plane. (b) Its atmosphere is principally carbon dioxide. (c) Its mean density is between 5 and 6 g cm-3. (d) Its surface is not visible because of heavy cloud cover. Which one is it? 631. All major planets are of approximately spherical shape. The principal physical reason for this is (a) gravitational attraction of every element of the planet by every other element; (b) erosion by meteoric impacts; (c) the average gravitational effect of satellites of the planet; (d) gravitational attraction of every element of the planet by the Sun. 632. Discuss the fact that all large astronomical objects (e.g., the Sun, stars, and major planets) are approximately spherical whereas minor planets (asteroids), nuclei of comets, and small satellites of planets are of irregular shapes. Estimate the maximum radius of a rocky object that can have a markedly nonspherical shape. 633. Estimate the greatest physically possible height of a mountain on a solid-body planet. Compare your estimate with actual data on the Earth, Mars, and Venus (and the Moon). Other Planets, Their Satellites, and Rings / 83 634. Suppose that a tunnel is bored through the Earth in a straight line from New York to San Francisco and equipped so that a car can coast through it without friction or air resistance. Discuss the motion of the car after its release from rest at the mouth of the tunnel in New York. 635. Why is the deep interior material of a planet under high pressure? 636. The gross chemical constituency of a planet, an asteroid, or a planetary satellite is revealed by a single characteristic quantity. What is that quantity? 637. The mean density of a planetary body provides the most important single item of information on (a) its age; (b) its rate of rotation; (c) its internal composition; (d) its orbital speed. 638. The distinction between the terrestrial planets and the Jovian planets is based primarily on their (a) synodic periods of revolution ; (b) mean densities; (c) rotational periods; (d) diameters. 639. All but one of the following is a terrestrial (i.e., Earth-like) planet: (a) Mars; (b) Mercury; (c) Venus; (d) Saturn. 640. Name the five known outer planets of the solar system. 641. Which planet has the most prominent system of rings? 642. An astronomer reports the discovery of a planet of the brightness of Uranus moving northward through the constellation Ursa Major at the rate of five degrees per year. A tentative professional assessment of this report would include all but one of the following...